Ranging Behavior and Spatial Cognition of Howler Monkeys

Abstract

Since the first long-term field study of mantled howler monkeys carried out by Clarence R. Carpenter on Barro Colorado Island about 80 years ago, howler movement patterns and range use have been studied in several species and study sites throughout Mexico, Central, and South America. Howler monkeys often use small home ranges (<30 ha) and travel short distances each day (<1,000 m) compared with other atelines. Home range size, day range length, and patterns of use of space may vary both within- and between-species in response to differences in forest structure, patterns of resource distribution and phenology, the area of habitat available, group size, and population density. Within-species variability has been shown to increase with increasing sample size. In addition, howlers present a pattern of repetitive use of a limited number of routes to travel between feeding and sleeping sites that has been related to a strategy aimed at reducing the distance travelled while allowing them to keep track of the phenology of important food sources. In this chapter we present the results of a comprehensive review of the literature on the ranging behavior of Alouatta (spp.). We used Generalized Linear Models (GLMs) to test whether home range is affected by (1a) fragment size, (1b) population density, (1c) group size, and (1d) group biomass, and whether day range is affected by (2a) fragment size, (2b) population density, (2c) group size, and the contribution of (2d) fruits and (2e) leaves to the diet. We also included species and method of estimating home range as factors in the models. We found that the size of the home range is negatively influenced by population density, and that there are differences between species (A. palliata uses significantly larger home ranges), and estimating methods. We also found that the length of the day range is negatively affected by population density, and the contribution of fruits and leaves to the diet, but positively affected by group size. Interspecific comparisons showed that A. guariba clamitans tends to travel farther daily than A. palliata. Cognitively, recent evidence supports the idea that howler monkeys are capable of encoding, processing, updating, and recalling a topological spatial representation of a set of landmarks (including major feeding and resting sites) as prominent beacons for navigating along commonly used routes within their home ranges.